Butter warmer



FIG. 1 is a top perspective view of a butter warmer showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a side elevational view thereof as seen from the front or rear of FIG. 1;

FIG. 4 is a side elevational view thereof as seen from the right or left of FIG. 1; and

FIG. 5 is a bottom plan view thereof. 

The ornamental design for a butter warmer, as shown. 